1. Field of the Invention
The present invention relates to a novel cyclic dione polymer, and more particularly relates to a novel cyclic dione polymer that is suitable for use in thin film coating and photoresist technology.
2. Description of the Prior Art
Nowadays, thin film coating and photoresist technology play very important roles in chemical engineering technology. A resin suitable for thin film coating should meet the requirements of not only having good film properties and good adherence to substrates, but also having good stability over a long storage time and low moisture absorbability. Therefore, a suitable resin should not have too many functional groups of high moisture absorbability. To be considered for application in IC photoresists, a suitable resin should further have other properties such as high etch and heat resistance, properties which are frequently achieved by molecular design.
To date, the most frequently used resin for thin film coating is the copolymer of a maleic anhydride derivative and norbornene, which has been disclosed in U.S. Pat. No. 3,928,497. Such a resin is suitable for being applied in IC photoresists because it has a broad processing window and linear relationship. However, since maleic anhydride easily absorbs moisture to form acid molecules, it has an inferior shelf life. Moreover, when the humidity in the air varies greatly, the E.sub.0 (photo speed) and .gamma. (contrast) will be difficult to be controlled; therefore, a stable line width of good properties can not be obtained. Since the disadvantage of high absorbability of said resin is due to its chemical structure, incorporating a plastisizer of low moisture absorbability is the only way to date of decreasing the absorbability of the maleic anhydride derivative/norbornene copolymer. In addition, said copolymer has other disadvantages: the glass transition temperature is too high, the film properties are inferior, and the film will easily crack.